National Archives. Washington, D.C., Nov. 22. Preservation of documents has long been a problem in libraries and offices of record. It was once done by a process known as 'crepelining,' which consisted in placing coarsely woven silk over and under the paper to be preserved with the use of adhesive. The most modern process now used is called the laminating process and consists in sandwiching the document between two sheets of thin, transparent cellulose acetate. This is then placed between two highly polished metal plates and subjected to heat and pressure in a hydraulic press